Variable Capacity Compressor

ABSTRACT

A variable capacity compressor including swash plate connected to rotor via link mechanism can calculate a moment of rotational motion acting on swash plate and set the total moment of rotational motion in inclination angle increasing direction acting on swash plate at minimum inclination angle to a small value. The shape or the like of swash plate  111  or the like are set so that moment M RX +M S  becomes a moment which orients swash plate in inclination angle increasing direction in a range from θmin (0°) to θb and becomes a moment which orients swash plate in inclination angle decreasing direction in a range from an inclination angle exceeding θb to θmax. The moment acting in inclination angle increasing direction of swash plate by setting the shape or the like of link arm  121  or the like is determined by calculating the sum of moment components.

TECHNICAL FIELD

The present invention relates to a variable capacity compressor for usein a vehicle air-conditioning system or the like.

BACKGROUND ART

There is known a variable capacity compressor which variably controls adischarge capacity by changing the stroke amount of a piston rotatingsynchronously with a drive shaft and reciprocating with a variableinclination angle (angle of inclination) relative to the axis line ofthe drive shaft.

In this type of variable capacity compressor, a moment in an inclinationangle increasing direction acts on a swash plate due to a reciprocatinginertia force of the piston. In order to counteract the moment, however,generally a product of inertia of the swash plate is set so that amoment of rotational motion in an inclination angle decreasing directionacts on the swash plate by the rotation of the swash plate.

At the minimum inclination angle or in the vicinity of the minimuminclination angle of the swash plate, however, the product of inertia ofthe swash plate is sometimes set so that the moment of rotational motionin the inclination angle increasing direction acts on the swash plate bythe rotation of the swash plate for a specific purpose.

In Patent Document 1, a large product of inertia of the swash plate isset at the minimum inclination angle 0° in order to use the inclinationangle increasing moment caused by the rotational motion of the swashplate for capacity recovery in a positive manner. On the other hand, inPatent Document 2, a relatively small product of inertia of the swashplate is set at the minimum inclination angle 0° in order to reduce theinclination angle increasing moment caused by the rotational motion ofthe swash plate so as to reduce power consumption during compressor offtime.

CITATION LIST Patent Documents

Patent Document 1: Japanese Laid-Open Patent Application Publication No.H07-293429

Patent Document 2: Japanese Laid-Open Patent Application Publication No.2000-2180

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

During the rotation of the drive shaft, the moment of rotational motionacting on the swash plate is able to be calculated by a formula such as,for example, one disclosed in Patent Document 1, with respect to theswash plate and a member that is fixed to the swash plate.

For a variable capacity compressor, however, having a structure in whicha link arm is not fixed to the swash plate and rotates about a firstconnecting pin (pin 11) when the inclination angle of the swash platechanges, for example, as disclosed in Japanese Laid-Open PatentApplication Publication No. 2002-188565, the formula disclosed in PatentDocument 1 is not enough to calculate the total moment of rotationalmotion acting on the swash plate including an influence of the link arm.Therefore, conventionally, for example, the total moment has beencalculated in consideration of only an inclination angle increasingmoment caused by a centrifugal force of the link arm, which therebycauses a gap between the calculated value and the actual value in thetotal moment of rotational motion acting on the swash plate during therotation of the drive shaft.

The present invention has been made in view of the above conventionalproblem. Therefore, it is an object of the present invention to providea variable capacity compressor in which a swash plate and a rotor areconnected to each other via a link mechanism with both ends rotatablyconnected to the swash plate and the rotor, the variable capacitycompressor capable of accurately calculating the total moment ofrotational motion acting on the swash plate including an influence of alink arm and setting the total moment of rotational motion in aninclination angle increasing direction acting on the swash plate at theminimum inclination angle to a relatively small value.

Means for Solving the Problems

Therefore, according to claim 1 of the present invention, there isprovided a variable capacity compressor which variably controls adischarge capacity of refrigerant by connecting a rotor fixed to a driveshaft rotatably supported within a housing to a swash plate slidablyattached to the drive shaft so that an inclination angle relative to anaxis line of the drive shaft is variable via a link arm with both endsrotatably connected to the rotor and the swash plate, allowing tiltingof the swash plate while causing the swash plate to rotate synchronouslywith the rotor, converting the rotation of the swash plate toreciprocating motion parallel to the drive shaft of a piston insertedinto a cylinder bore to draw and discharge the refrigerant, andcontrolling the inclination angle of the swash plate to control a strokeamount of the piston, having the following configuration.

A shape, weight, and center of gravity of the swash plate, or those ofthe swash plate and a connected body integral therewith, are set so thata moment of rotational motion caused by the swash plate, or the swashplate and the connected body integral therewith, when the drive shaftrotates in the position of a minimum inclination angle θmin of the swashplate acts in an inclination angle decreasing direction of the swashplate.

A shape, weight, and center of gravity of the link arm, or those of thelink arm and a connected body integral therewith, are set so that atotal moment of rotational motion caused by the link arm, the swashplate, and the connected body integral therewith acts in an inclinationangle increasing direction of the swash plate.

The moment of rotational motion acting in the inclination angleincreasing direction of the swash plate by setting the shape, weight,and center of gravity of the link arm, or those of the link arm and theconnected body integral therewith, is determined by calculating a sum ofmoment components about the center of gravity and moment componentscaused by a centrifugal force acting on the center of gravity.

Moreover, the invention according to claim 2 has the followingconfiguration: a minimum inclination angle θmin of the swash plate isset to 0° supposing that the inclination angle of the swash plate is 0°when the swash plate is orthogonal to the axis line of the drive shaft;and the moment of rotational motion caused by the link arm, the swashplate, and the connected body integral therewith acts in the inclinationangle increasing direction of the swash plate in a range from theminimum inclination angle θmin to a predetermined inclination angle θband acts in the inclination angle decreasing direction of the swashplate in a range from an inclination angle just exceeding thepredetermined inclination angle θb to a maximum inclination angle Amax;and the predetermined inclination angle θb is set to a minimuminclination angle range where a compression reaction force is appliedwhen the piston compresses the refrigerant.

Effect of the Invention

According to the invention of claim 1, the total moment of rotationalmotion in the inclination angle increasing direction acting on the swashplate at the minimum inclination angle of the swash plate is able to beset small and accurately, thereby improving the control accuracy of theinclination angle of the swash plate in the vicinity of the minimuminclination angle of the variable capacity compressor.

According to the invention of claim 2, the moment of rotational motionin the inclination angle increasing direction acting on the swash plateacts only on the minimum inclination angle region and the inclinationangle smoothly increases when the inclination angle of the swash plateis less than θb, while sufficiently securing an inclination angle region(θ>θb) corresponding to a counter moment of a moment caused by aninertia force of a reciprocating motion of a piston or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating an internal structure of avariable capacity compressor according to the present invention.

FIGS. 2A and 2B are a side view and a drawing of view A, respectively,of a link arm used in the variable capacity compressor.

FIG. 3 is a perspective view of an assembly of a drive shaft and a rotorused in the variable capacity compressor.

FIG. 4 is a perspective view of a swash plate used in the variablecapacity compressor.

FIG. 5 is a view illustrating a coordinate system used to calculate amoment of rotational motion with respect to an assembly of the driveshaft, the rotor, the swash plate, and the link arm used in the variablecapacity compressor.

FIG. 6 is a view illustrating a X″Y″Z″ coordinate system of the linkarm.

FIG. 7 is a view used to calculate the center-of-gravity location G(G_(Y), G_(Z)) of the link arm.

FIG. 8 is a diagram illustrating respective moments of rotational motionacting on the swash plate.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be describedwith reference to drawings. FIG. 1 illustrates an internal structure ofa variable capacity compressor according to the present invention.

A variable capacity compressor 100, which is a clutchless compressor,includes a cylinder block 101 having a plurality of cylinder bores 101 ain a peripheral portion, a front housing 102 connected to one end of thecylinder block 101, and a cylinder head 104 connected to the other endof the cylinder block 101 via a valve plate 103.

A drive shaft 110 is provided across a crank chamber 140, which isdefined by the cylinder block 101 and the front housing 102, and a swashplate 111 is disposed around the axial center of the drive shaft 110.The swash plate 111 is connected to a rotor 112 fixed to the drive shaft110 via a link mechanism 120 and an inclination angle (the angle ofinclination) relative to the axis line of the drive shaft 110 isvariable.

Between the rotor 112 and the swash plate 111, there is mounted aninclination angle decreasing spring 114 which biases the swash plate 111toward the minimum inclination angle up to the minimum inclinationangle. On the opposite side of the swash plate 111, there is mounted aninclination angle increasing spring 115 which biases the swash plate 111in a direction of increasing the inclination angle of the swash plate111. The biasing force of the inclination angle increasing spring 115 isset larger than the biasing force of the inclination angle decreasingspring 114 at the minimum inclination angle, by which the swash plate111 is located at an inclination angle larger than the minimuminclination angle when the drive shaft 110 does not rotate and thebiasing force of the inclination angle decreasing spring 114 is balancedwith the biasing force of the inclination angle increasing spring 115.

One end of the drive shaft 110 passes through a boss portion 102 aprojecting outward of the front housing 102 so as to extend to theoutside thereof and is connected to a power transmission device, whichis not illustrated. In addition, a shaft seal device 130 is insertedbetween the drive shaft 110 and the boss portion 102 a to block theinside from the outside.

The drive shaft 110 and the rotor 112 are supported by bearings 131 and132 in a radial direction and supported by a bearing 133 and a thrustplate 134 in a thrust direction.

Then, the power from an external drive source such as a vehicle engineis transmitted to the power transmission device, and the drive shaft 110is rotatable in synchronization with the rotation of the powertransmission device. Incidentally, a gap between an abutting portion ofthe drive shaft 110 abutting against the thrust plate 134 and the thrustplate 134 is adjusted to a predetermined gap by using an adjustmentscrew 135.

A piston 136 is disposed in a cylinder bore 101 a, an outer peripheralportion of the swash plate 111 is accommodated in a recess, which isformed in the inside of the end of the piston 136 projecting toward thecrank chamber 140, and the swash plate 111 works with the piston 136 viaa pair of shoes 137. Therefore, the rotation of the swash plate 111enables the piston 136 to reciprocate within the cylinder bore 101 a.

In the cylinder head 104, a suction chamber 141 and a discharge chamber142 circularly enclosing the suction chamber 141 are divisionally formedin the center portion. The suction chamber 141 communicates with thecylinder bore 101 a via a communication hole 103 a and a suction valve(not illustrated) provided in the valve plate 103. The discharge chamber142 communicates with the cylinder bore 101 a via a discharge valve (notillustrated) and a communication hole 103 b which is formed in the valveplate 103.

A compressor housing is formed by fastening the front housing 102, thecylinder block 101, the valve plate 103, and the cylinder head 104 via agasket, which is not illustrated, by using a plurality of through bolts105.

Moreover, a muffler is provided in the upper part of the cylinder block101 in the view. The muffler is formed by fastening a cover member 106and a formed wall 101 b, which is divisionally formed in the upper partof the cylinder block 101, via a seal member, which is not illustrated,by using bolts. A check valve 200 is disposed in a muffler space 143.The check valve 200 is disposed in a connection between a communicationpassage 144 and the muffler space 143. The check valve 200 operates inresponse to a pressure difference between the communication passage 144(on the upstream side) and the muffler space 143 (on the downstreamside): closes the communication passage 144 if the pressure differenceis less than a predetermined value; and opens the communication passage144 if the pressure difference is more than the predetermined value.Therefore, the discharge chamber 142 is connected to a discharge-siderefrigerant circuit of the air-conditioning system via a dischargepassage formed of the communication passage 144, the check valve 200,the muffler space 143, and a discharge port 106 a.

In the cylinder head 104, a suction port 104 a and a communicationpassage 104 b are formed, and the suction chamber 141 is connected to asuction-side refrigerant circuit of the air-conditioning system via asuction passage formed of the communication passage 104 b and thesuction port 104 a. The suction passage extends in a straight lineacross a part of the discharge chamber 142 from the outside in theradial direction of the cylinder head 104.

The cylinder head 104 is further provided with a control valve 300. Thecontrol valve 300 controls an introduction amount of discharge gas intothe crank chamber 140 by adjusting the opening degree of a communicationpassage 145, which communicates between the discharge chamber 142 andthe crank chamber 140. Moreover, the refrigerant in the crank chamber140 flows into the suction chamber 141 through a communication passage101 c, a space 146, and an orifice 103 c formed in the valve plate 103.

Accordingly, the control valve 300 is able to variably control thedischarge capacity of the variable capacity compressor 100 by varyingthe pressure of the crank chamber 140, i.e., the back pressure of thepiston 136 and changing the inclination angle of the swash plate 111,i.e., the stroke amount of the piston 136.

During air conditioning operation, i.e., in the operating state of thevariable capacity compressor 100, the amount of current to a solenoidbuilt in the control valve 300 is adjusted on the basis of an externalsignal, and the discharge capacity is variably controlled so that thepressure of the suction chamber 141 is at a predetermined value. Thecontrol valve 300 is able to optimally control the suction pressureaccording to an external environment.

During non-air conditioning operation, i.e., in the non-operating stateof the variable capacity compressor 100, the communication passage 145is forcibly opened by turning off the current to the solenoid built inthe control valve 300 to control the discharge capacity of the variablecapacity compressor 100 to the minimum.

Subsequently, the link mechanism 120 according to the present inventionwill be described.

The rotor 112 is fixed to the drive shaft 110 and the rotor 112 isprovided with a pair of first arms 112 a projecting toward the swashplate 111 side in parallel with the drive shaft 110. One end 121 a,which is formed substantially in a cylindrical shape, of the link arm121 is guided into the inside of the pair of first arms 112 a.

Specifically, a first connecting pin 122 as a connecting means isinserted into a through hole 112 b formed in a first arm 112 a and intoa through hole 121 b formed in one end 121 a of the link arm 121, bywhich the link arm 121 is rotatable about the axis line of the firstconnecting pin 122 while being guided by the pair of first arms 112 a.

In addition, the first connecting pin 122 is press-fitted and retainedin the through hole 121 b formed in the link arm 121 and a minute gap isformed between the outer periphery of the first connecting pin 122 andthe through hole 112 b which is formed in the first arm 112 a, therebyenabling a relative rotation.

The other end 121 c of the link arm 121 has a pair of arms projectedfrom one end 121 a which is formed in a cylindrical shape, and a secondarm 111 a which is projected from the swash plate 111 is guided into theinside of the arms. A second connecting pin 123 as a connecting means isinserted into the through hole 121 d formed at the other end 121 c ofthe link arm 121 and the through hole 111 b formed in the second arm 111a, by which the link arm 121 is connected to the swash 111, thusenabling the link arm 121 and the swash plate 111 to relatively rotateabout the axis of the second connecting pin 123.

In addition, the second connecting pin 123 is press-fitted and retainedin the through hole 111 b of the second arm 111 a and a minute gap isformed between the outer periphery of the second connecting pin 123 andthe through hole 121 d which is formed in the link arm 121, therebyenabling a relative rotation.

The link mechanism 120 is composed of the first arm 112 a, the secondarm 111 a, the link arm 121, the first connecting pin 122, and thesecond connecting pin 123. Therefore, the swash plate 111 is connectedto the rotor 112 fixed to the drive shaft 110 via the link mechanism 120so as to receive a rotational torque of the rotor 112, by which theinclination angle of the swash plate 111 is variable along the driveshaft 110.

A through hole 111 c of the swash plate 111, which is formed passingthrough the drive shaft 110, is formed in a shape where the swash plate111 is able to tilt within a range from the maximum inclination angle(Amax) to the minimum inclination angle (θmin). Specifically, thethrough hole 111 c includes a maximum inclination angle restrictingportion for restricting the maximum inclination angle by abuttingagainst the drive shaft 110 and a minimum inclination angle restrictingportion for restricting the minimum inclination angle in the samemanner.

Supposing that the inclination angle of the swash plate is set to 0°when the swash plate 111 is orthogonal to the drive shaft 110, theminimum inclination angle restricting portion of the through hole 111 cis formed so that the swash plate 111 is able to be displaced up tosubstantially 0° in the inclination angle. In addition, the term,“substantially 0°” means a range of 0°±0.5°.

Regarding the variable capacity compressor constructed as describedabove, the following describes a moment related to the inclination angleof the swash plate 111.

First, the calculation of the moment of rotational motion caused by thelink arm acting on the swash plate 111 will be described with referenceto FIGS. 5 to 7.

When the connecting portion such as the first connecting pin 122 forconnecting the link arm 121 to the rotor is fixed to the link arm 121side, the moment is calculated as a moment of a connected body betweenthe link arm 121 and the connecting portion such as the first connectingpin 122. Moreover, also when the connecting portion such as the secondconnecting pin for connecting the link arm 121 to the swash plate 111 isfixed to the link arm 121 side, the moment is calculated as a moment ofa connected body between the link arm 121 and the connecting portionsuch as the second connecting pin 123 in the same manner.

a. Coordinate System

In an assembly of the drive shaft 110, the rotor 112, the swash plate111, and the link mechanism 120 of the variable capacity compressor 100,three coordinate systems (XYZ, X′Y′Z′, X″Y″Z″) will be discussed asillustrated in FIGS. 5 and 6.

The first is an XYZ coordinate system with the axis of the drive shaft110 as the Z axis in a plane including the axis of the drive shaft 110and the center axis line of the piston 136 located at a top dead centerposition, a line passing through the center of the first connecting pin122 and orthogonal to the axis of the drive shaft 110 as the Y axis, anda line passing through the intersection of the Z axis and the Y axis andorthogonal to the Z axis and the Y axis as the X axis.

The second is an X′Y′Z′ coordinate system with the origin at the centerof gravity G of the link arm 121, having an X′ axis parallel to the Xaxis, a Y′ axis parallel to the Y axis, and a Z′ axis parallel to the Zaxis. In addition, the link arm 121 has a symmetrical shape with respectto a plane including the axis of the drive shaft 110 and the center axisline of the piston 136 located at the top dead center position and alsohas a symmetrical shape with respect to a plane orthogonal to the aboveplane and passing through the center of the through hole 121 b (i.e.,the first connecting pin 122) and the center of the through hole 121 d(i.e., the second connecting pin 123). Therefore, the center of gravityG is located in a YZ plane and on a line passing through the center ofthe first connecting pin 122 and the center of the second connecting pin123.

The third is an X″Y″Z″ coordinate system with the origin at the centerof gravity G of the link arm and with a line passing through the centerof the first connecting pin 122 and the center of the second connectingpin 123 as the Z″ axis in a plane including the axis of the drive shaft110 and the center axis line of the piston 136 located at the top deadcenter position, an axis orthogonal to the Z″ axis as the Y″ axis, andan axis line orthogonal to the Z″ axis and the Y″ axis as the X″ axis.

The link arm 121 rotates about the first connecting pin 122 in the YZplane according to the displacing operation of the swash plate 111 andthe position of the second connecting pin 123 changes accordingly. Theangle of inclination β of the link arm 121 in the case of theinclination angle θ of the swash plate 111 is an angle between the Y″axis and the Z″ axis.

b. Moment about Center of Gravity G of Link Arm

When the rotor 112 rotates, a moment of rotational motion acts about thefirst connecting pin 122 connected to the rotor 112 by the link arm 121.

The moment vector M_(L) about the first connecting pin 122 is the timederivative of the angular momentum H_(L) and therefore expressed by thefollowing equation.

[Math. 1]

M _(L) ={dot over (H)} _(L) ={dot over (H)} _(GL) +r×ma  (1)

where:

{dot over (H)}_(GF): Moment vector about center of gravity of link arm

r: Position vector of center of gravity of link arm relative to centerof first connecting pin

m: Weight of link arm

a: Acceleration vector of center of gravity of link arm

Since the link arm 121 is symmetrical as described above, the principalaxis of inertia coincides with the X″Y″Z″ axis. Therefore, the moment ofinertia tensor I_(L) is expressed by the following equation.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 2} \right\rbrack & \; \\{I_{L} = \begin{pmatrix}I_{X^{''}X^{''}} & 0 & 0 \\0 & I_{Y^{''}Y^{''}} & 0 \\0 & 0 & I_{Z^{''}Z^{''}}\end{pmatrix}} & (2)\end{matrix}$

If the equation (2) is coordinate-transformed to that in the X′Y′Z′coordinate system, the moment of inertia tensor I_(L)′ is expressed bythe following equation.

[Math. 3]

(_(L) ′=RI _(L) R ⁻¹  (3)

R: Rotation matrixTherefore, the angular momentum vector H_(GL) about the center ofgravity G is determined by the following equation.

$\begin{matrix}{\mspace{79mu} \left\lbrack {{Math}.\mspace{14mu} 4} \right\rbrack} & \; \\\begin{matrix}{H_{GL} = {I_{L}^{\prime}\omega}} \\{= {{RI}_{L}R^{- 1}\omega}} \\{= {\begin{pmatrix}1 & 0 & 0 \\0 & {\cos \; \beta} & {\sin \; \beta} \\0 & {{- \sin}\; \beta} & {\cos \; \beta}\end{pmatrix}\begin{pmatrix}I_{X^{''}X^{''}} & 0 & 0 \\0 & I_{Y^{''}Y^{''}} & 0 \\0 & 0 & I_{Z^{''}Z^{''}}\end{pmatrix}}} \\{{\begin{pmatrix}1 & 0 & 0 \\0 & {\cos \; \beta} & {{- \sin}\; \beta} \\0 & {\sin \; \beta} & {\cos \; \beta}\end{pmatrix}\begin{pmatrix}0 \\0 \\\omega_{Z}\end{pmatrix}}} \\{= \begin{pmatrix}0 \\{\frac{1}{2}{\omega_{Z}\left( {I_{Z^{''}Z^{''}} - I_{Y^{''}Y^{''}}} \right)}\sin \; 2\beta} \\{\omega_{Z}\left( {{I_{Y^{''}Y^{''}}\sin^{2}\beta} + {I_{Z^{''}Z^{''}}{\cos^{2}(\beta)}}} \right)}\end{pmatrix}}\end{matrix} & (4)\end{matrix}$

-   -   ω_(z): Rotational angular velocity of drive shaft

Therefore, the moment M_(GL) about the center of gravity is obtained bythe following equation.

$\begin{matrix}\begin{matrix}{M_{GL} = {\overset{.}{H}}_{GL}} \\{= {{- \omega} \times H_{GL}}} \\{= {\begin{pmatrix}0 \\0 \\{- \omega_{Z}}\end{pmatrix}\begin{pmatrix}0 \\{\frac{1}{2}{\omega_{Z}\left( {I_{Z^{''}Z^{''}} - I_{Y^{''}Y^{''}}} \right)}\sin \; 2\beta} \\{\omega_{Z}\left( {{I_{Y^{''}Y^{''}}\sin^{2}\beta} + {I_{Z^{''}Z^{''}}{\cos^{2}(\beta)}}} \right)}\end{pmatrix}}} \\{= \begin{pmatrix}{\frac{1}{2}{\omega_{Z}^{2}\left( {I_{Z^{''}Z^{''}} - I_{Y^{''}Y^{''}}} \right)}\sin \; 2\beta} \\0 \\0\end{pmatrix}}\end{matrix} & (5)\end{matrix}$

c. Moment Caused by Centrifugal Force Acting on Center of Gravity ofLink Arm

The second term r×ma in the equation (1) is the cross product of aposition vector and a force vector, which is a moment of force.

Since the link arm 121 rotates about the first connecting pin 122 in theYZ plane, the moment vector is oriented in the X-axis direction.

Therefore, the force ma is a centrifugal force applied to the center ofgravity and r is a distance between the center of the second connectingpin and the center of gravity of the link arm in the Z-axis direction.

The center-of-gravity location G (G_(Y), G_(Z)) of the link arm 121 isable to be determined as follows with reference to FIG. 7.

G _(Y) =L _(Y) +L _(G) cos β

G _(Z) =L _(G) sin β  [Math. 6]

Therefore, the centrifugal force F_(C) and the moment M_(FL) about thefirst connecting pin 122 caused by the centrifugal force F_(C) are ableto be determined by the following equation.

[Math. 7]

F _(C) =mG _(Y)ω_(Z) ² =m(L _(Y) +L _(G) cos β)ω_(Z) ²

M _(FL) =r×ma=−F _(C) G _(Z) =−mL _(G) sin β(L _(Y) +L _(G) cos β)ω_(Z)²  (6)

d. Moment of Rotational Motion Caused by Link Arm about First ConnectingPin

The moment M_(L) of rotational motion caused by the link arm 121 aboutthe first connecting pin 122 is able to be determined by the followingequation from the equations (1), (5), and (6).

$\begin{matrix}{\mspace{79mu} \left\lbrack {{Math}.\mspace{14mu} 8} \right\rbrack} & \; \\\begin{matrix}{M_{L} = {M_{GL} + M_{FL}}} \\{= {\begin{pmatrix}{\frac{1}{2}{\omega_{Z}^{2}\left( {I_{Z^{''}Z^{''}} - I_{Y^{''}Y^{''}}} \right)}\sin \; 2\beta} \\0 \\0\end{pmatrix} + \begin{pmatrix}{{\frac{1}{2}{\omega_{Z}^{2}\left( {I_{Z^{''}Z^{''}} - I_{Y^{''}Y^{''}}} \right)}\sin \; 2\beta} -} \\{{mL}_{G}\sin \; {\beta \left( {L_{Y} + {L_{G}\cos \; \beta}} \right)}\omega_{Z}^{2}} \\0 \\0\end{pmatrix}}}\end{matrix} & (7) \\{{\therefore M_{LX}} = {\omega_{Z}^{2}\left\{ {{\frac{1}{2}\left( {I_{Z^{''}Z^{''}} - I_{Y^{''}Y^{''}}} \right)\sin \; 2\beta} - {{mL}_{G}\sin \; {\beta \left( {L_{Y} + {L_{G}\cos \; \beta}} \right)}}} \right\}}} & \;\end{matrix}$

e. Moment of Link Arm about Instant Center of Swash Plate Displacing

The instant center of swash plate displacing R_(C) is the intersectionof a line passing through the center of rotation K of the swash plate111 in the YZ plane and orthogonal to the Z axis and a line passingthrough the center of the first connecting pin 122 and the center of thesecond connecting pin 123.

The product of a force F_(R) in the rotational direction of the secondconnecting pin 123, which is generated by the moment M_(LX) about thefirst connecting pin 122, and a distance L_(R) between the center of thesecond connecting pin and the instant center is a moment M_(RX) aboutthe instant center of swash plate displacing R_(C) caused by the linkarm 121, and the moment M_(RX) is able to be determined by the followingequation.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 9} \right\rbrack & \; \\{{F_{R} = \frac{M_{LX}}{L_{P}}}\begin{matrix}{M_{RX} = {F_{R}L_{R}}} \\{= {\frac{L_{R}}{L_{P}}M_{LX}}}\end{matrix}} & (8)\end{matrix}$

L_(P): Distance between center of first connecting pin and center ofsecond connecting pin

Moment of Changing Inclination Angle of Swash Plate (FIG. 8)

As described above, the swash plate 111 controls the discharge capacityby changing the inclination angle of the swash plate 111 by controllingthe pressure of the crank chamber 140 acting on the piston 136 againstthe inclination angle increasing moment caused by a gas compressionreaction force of the piston 136 by using the control valve 300. Themoments described below act on the change in the inclination angle ofthe swash plate 111. Specifically, the moments include a moment causedby a resultant force between a biasing force of the coil spring 114 anda biasing force of the coil spring 115, a moment M_(P) caused by aninertia force generated by reciprocating motion of the piston 136 or thelike, and a moment M_(R) of rotational motion acting on the swash plate111.

Incidentally, the moment M_(P) and the moment M_(R) increase inproportion to the square of the rotational speed of the drive shaft 110and therefore are almost negligible in a region in which the rotationalspeed is low, while affecting the change in the inclination angle of theswash plate 111 in a region of high rotational speed.

The moment M_(P) acts in the inclination angle increasing direction,while the moment M_(R) is basically a counter moment of the momentM_(P), though the moment M_(R) acts in the inclination angle increasingdirection in a region of a small inclination angle.

FIG. 8 illustrates the moments of rotational motion acting on the swashplate 111 at a predetermined rotational speed of the drive shaft.

The second connecting pin 123 is press-fitted into the swash plate 111,and the moment M_(S) of the rotational motion generated by the rotationof the swash plate 111 on the basis of the setting of the product ofinertia of the swash plate 111 includes that of the second connectingpin 123. Thus, the shape, weight, and center of gravity of the swashplate 111 are set so as to have the characteristics illustrated by M_(S)in FIG. 8. Specifically, the integral construction of the secondconnecting pin 123 and the swash plate 111 is set so as to cause amoment of rotational motion which orients the swash plate 111 in theinclination angle decreasing direction at the minimum inclination angleθmin (0°) (M_(S)<0).

In addition, if the connecting member such as the second connecting pinor the like is secured to the link arm 121, the moment M_(S) iscalculated as a moment of the swash plate 111 only.

When the rotor 112 rotates, the link arm 121 causes the moment ofrotational motion acting about the first connecting pin 122. Asillustrated in FIG. 8, the moment serves as a moment M_(RX) ofrotational motion which orients the swash plate 111 in the inclinationangle increasing direction via the second connecting pin 123 (M_(RX)>0).

Therefore, the moment M_(R) of rotational motion acting on the swashplate 111 is calculated by M_(S)+M_(RX).

The shape, weight, and center of gravity of the link arm 121 are set soas to satisfy M_(S)+M_(RX)>0 at the minimum inclination angle θmin (0°),here.

Thus, the assembly where the link arm 121 is connected to the integralconstruction of the second connecting pin 123 and the swash plate 111receives the moment of rotational motion which orients the swash plate111 in the inclination angle increasing direction in a range from theminimum inclination angle θmin (0°) to an inclination angle θb, whilethe assembly receives the moment of rotational motion which orients theswash plate 111 in the inclination angle decreasing direction in a rangefrom an inclination angle just exceeding the inclination angle θb to themaximum inclination angle (θmax).

Although being set so as to satisfy M_(S)+M_(RX)>0, the shape, weight,center of gravity of the link arm 121 are set so as to minimize theinfluence of M_(S)+M_(RX) as possible.

The moment M_(S)+M_(RX) of the rotational motion, which orients theswash plate 111 in the inclination angle increasing direction,contributes to increasing the inclination angle of the swash plate fromthe region of less than the inclination angle θb, but when theinclination angle reaches an inclination angle region where thecompression reaction force is generated when the piston 136 compressesthe gas, the moment M_(S)+M_(RX) is no longer needed. Therefore, theinclination angle θb is set to the minimum inclination angle regionwhere the compression reaction force is generated when the piston 136compresses the gas. Specifically, the inclination angle θb is set to aninclination angle region which causes the discharge capacity to bewithin a range of 2% to 5% where the maximum discharge capacitycorresponding to the maximum inclination angle θmax is 100%.

Accordingly, if the inclination angle of the swash plate 111 is lessthan θb, for example when the variable capacity compressor 100 is run inthe non-operating state, switching the variable capacity compressor 100from this state to the operating state causes the moment M_(S)+M_(RX) ofrotational motion to assist the increase in the inclination angle of theswash plate caused by the biasing force of the coil spring 115, by whichthe inclination angle of the swash plate is smoothly increased. Inaddition, if the inclination angle of the swash plate 111 exceeds θb,the moment M_(S)+M_(RX) of rotational motion immediately serves as thecounter moment of the moment M_(P) caused by an inertia force tocontribute to decreasing the moment imbalance.

Since the moment of rotational motion in the inclination angleincreasing direction acting on the swash plate 111 is limited to therange of 2% to 5% in the discharge capacity, an adverse effect caused bythe moment of rotational motion in the inclination angle increasingdirection can be substantially avoided even in the case where thevariable capacity compressor 100 rotates at high speed.

In this manner, the moment of rotational motion in the inclination angleincreasing direction acting on the swash plate acts only on a requiredminimum inclination angle region, thereby smoothly increasing theinclination angle in the case where the inclination angle of the swashplate is less than θb and sufficiently securing the inclination angleregion (θ>θb) corresponding to the counter moment of the moment causedby an inertia force generated by reciprocating motion of the piston orthe like.

The above configuration is achieved, as described in the aforementionedmoment calculation process, by making settings so that the link arm 121causes the moment M_(LX) of rotational motion acting about the firstconnecting pin 122 and the moment M_(LX) serves as the moment M_(R)(substantially constant regardless of a change in the inclination angleas illustrated in FIG. 8) in the inclination angle increasing directionof the swash plate 111 to act via the connection between the link arm121 and the swash plate 111, while the moment M_(S) of rotational motionis set so as to act in the inclination angle decreasing direction of theswash plate 111, where the moment M_(S) of rotational motion is causedby the swash plate 111 and the second connecting pin 123 when the driveshaft 110 rotates in the position of the minimum inclination angle θminof the swash plate 111.

Moreover, the moment M_(P)+M_(S)+M_(RX) arising from the drive shaftrotation is able to be maintained at a value close to zero with thesesettings, thereby minimizing an influence on the discharge capacitycontrol by the control of the pressure in the crank chamber 140 (backpressure of the piston 136) with the control valve 300 as possible andimproving the control accuracy.

If calculation is made in consideration of only the inclination angleincreasing moment caused by the centrifugal force of the link arm in asimple manner in the variable capacity compressor including the linkmechanism to be the target of the present invention, the total moment ofrotational motion when the drive shaft rotates cannot be accuratelycalculated. Particularly, as disclosed in Patent Document 2, in the caseof preventing an increase of the inclination angle increasing momentcaused by the rotational motion of the swash plate by setting a smallproduct of inertia of the swash plate at the minimum inclination angle,the influence of the inclination angle increasing moment acting on theswash plate by the link arm is relatively large, which causes theinclination angle of the swash plate to deviate from the target in thecase where the swash plate is located in the vicinity of the minimuminclination angle.

In this respect, in the above embodiment, the moment of rotationalmotion in the inclination angle increasing direction of the swash platewith the settings of the shape, weight, and center of gravity of thelink arm is determined by calculating the sum of the moment componentsabout the center of gravity of the link arm and the moment componentscaused by the centrifugal force acting on the center of gravity of thelink arm, by which the moment of rotational motion is able to beaccurately calculated.

This enables accurate settings of the inclination angle of the swashplate in the vicinity of the minimum inclination angle, thereby enablinghigh-accuracy control of the discharge capacity of refrigerantrepresented by the control characteristic of the inclination angle,i.e., the stroke amount of the piston.

Although the link arm is a single member in the above embodiment, thelink arm may include a plurality of members.

Moreover, the link arm is symmetrical in shape in the above embodiment,but may be asymmetrical in shape.

Furthermore, although the connecting means of the link arm is a pin inthe above embodiment, the link arm may have a structure without the useof a pin or pins. For example, a structure where the tip of one end ofthe link arm is rotatably supported may be provided on the rotor sidewithout using the first connecting pin.

Furthermore, although the swash plate is directly supported by the driveshaft in the above embodiment, the swash plate may be supported by aswash plate support (sleeve) slidably fitted to the drive shaft in analternative swash plate structure.

Moreover, the minimum inclination angle restricting portion is formed inthe through hole 111 c of the swash plate in the embodiment, but acirclip or the like may be attached to the drive shaft to restrict theminimum inclination angle.

Although the clutchless compressor is used in the embodiment, thevariable capacity compressor may be equipped with an electromagneticclutch. Moreover, the present invention is also applicable to a variablecapacity compressor driven by a motor.

REFERENCE SIGNS LIST

-   100: Variable capacity compressor-   101: Cylinder block-   101 a: Cylinder bore-   102: Front housing-   104: Cylinder head-   110: Drive shaft-   111: Swash plate-   111 a: Second arm-   111 c: Through hole-   112: Rotor-   112 a: First arm-   114: Inclination angle decreasing spring-   115: Inclination angle increasing spring-   116: Spring support member-   116 a: Cylindrical portion-   120: Link mechanism-   121: Link arm-   122: First connecting pin-   123: Second connecting pin-   136: Piston-   140: Crank chamber-   141: Suction chamber-   142: Discharge chamber-   145: Communication passage-   300: Control valve-   M_(P): Moment caused by inertia force generated by reciprocating    motion of piston 136 or the like-   M_(RX): Moment of rotational motion acting on swash plate 111 by    link arm 121-   M_(S): Moment of rotational motion acting on swash plate 111 and    second connecting pin 123

1. A variable capacity compressor which variably controls a dischargecapacity of refrigerant by connecting a rotor fixed to a drive shaftrotatably supported within a housing to a swash plate slidably attachedto the drive shaft so that an inclination angle relative to an axis lineof the drive shaft is variable via a link arm with both ends rotatablyconnected to the rotor and the swash plate, allowing tilting of theswash plate while causing the swash plate to rotate synchronously withthe rotor, converting the rotation of the swash plate to reciprocatingmotion parallel to the drive shaft of a piston inserted into a cylinderbore to draw and discharge the refrigerant, and controlling theinclination angle of the swash plate to control a stroke amount of thepiston, wherein: a shape, weight, and center of gravity of the swashplate, or those of the swash plate and a connected body integraltherewith, are set so that a moment of rotational motion caused by theswash plate, or the swash plate and the connected body integraltherewith, when the drive shaft rotates in the position of a minimuminclination angle θmin of the swash plate acts in an inclination angledecreasing direction of the swash plate; a shape, weight, and center ofgravity of the link arm, or those of the link arm and a connected bodyintegral therewith, are set so that a total moment of rotational motioncaused by the link arm, the swash plate, and the connected body integraltherewith acts in an inclination angle increasing direction of the swashplate; and the moment of rotational motion acting in the inclinationangle increasing direction of the swash plate by setting the shape,weight, and center of gravity of the link arm, or those of the link armand the connected body integral therewith, is determined by calculatinga sum of moment components about the center of gravity and momentcomponents caused by a centrifugal force acting on the center ofgravity.
 2. The variable capacity compressor according to claim 1,wherein a minimum inclination angle θmin of the swash plate is set to 0°supposing that the inclination angle of the swash plate is 0° when theswash plate is orthogonal to the axis line of the drive shaft, and themoment of rotational motion caused by the link arm, the swash plate, andthe connected body integral therewith acts in the inclination angleincreasing direction of the swash plate in a range from the minimuminclination angle θmin to a predetermined inclination angle θb and actsin the inclination angle decreasing direction of the swash plate in arange from an inclination angle just exceeding the predeterminedinclination angle θb to a maximum inclination angle θmax, and thepredetermined inclination angle θb is set to a minimum inclination anglerange where a compression reaction force is applied when the pistoncompresses the refrigerant.